DBTDL (Dibutyltin Dilaurate, CAS 77-58-7): The Reference Tin Catalyst for Condensation-Cure Silicone and Polyurethane
SEMITECH stocks DBTDL at ≥97% purity (Sn 18.0–18.5%) — the highest-activity organotin catalyst specified at 0.05–0.5% in alkoxy/oxime-cure RTV sealants, RTV-2 condensation moulding, and polyurethane gel-time control. 25 kg HDPE jerrycan, nitrogen-blanketed, 2–4 week ex-China lead time.
Contents
| 77-58-7 | ≥97% | 25 kg |
|---|---|---|
| CAS number | Active content | MOQ (HDPE) |
Chemistry & Specifications
DBTDL (C₃₂H₆₄O₄Sn, MW 631.6) is a clear pale-yellow liquid, density 1.05 g/cm³, soluble in nearly all organic solvents and silicone fluids, insoluble in water. The bis-laurate ligand provides optimal Lewis acidity for catalysis while suppressing hydrolysis. SEMITECH specification: active content ≥97%, Sn 18.0–18.5% (ICP-OES), water ≤0.1% (Karl Fischer), APHA ≤100.
Cure Mechanism: Lewis-Acid Catalysis of Si-OH + Si-OR Condensation
DBTDL coordinates to the silanol oxygen, lowering the activation energy for crosslinker attack and releasing alcohol or oxime byproduct.
- Loading 0.05–0.15% — long-pot-life RTV-1 sealants
- Loading 0.15–0.30% — standard alkoxy-cure RTV-1 and RTV-2; tack-free 30–60 min at 23°C/50% RH
- Loading 0.30–0.50% — fast-cure RTV-1 for production-line bonding
- Loading 0.01–0.10% — polyurethane gel-time control
Warning: DBTDL poisons platinum addition-cure systems at ppm levels. Dedicated equipment is mandatory.
▶Show full content (5 sections)
Applications & Formulation Guidance
RTV-1 alkoxy-cure sealants (largest application): 0.10–0.20% with MTMS crosslinker gives 25–40 min tack-free time. RTV-1 oxime-cure: 0.15–0.30%. RTV-2 mould rubber: 0.15–0.50% with TEOS or ethyl-silicate-40 crosslinker. PU elastomer casting: 0.01–0.10% for gel-time control. Alkyd resin synthesis: 0.05–0.20% at 180–230°C for ester transesterification.
Procurement, Storage and Quality Control
CoA per batch: Sn assay, active content, water, APHA, refractive index. Packing: 25 kg HDPE jerrycans under nitrogen; 200 kg drums for bulk. Lead time 1–2 weeks to Asia, 4–6 weeks to Europe/Houston. Shelf life 12 months sealed below 25°C; opened drums consume within 60 days under nitrogen. REACH-registered for industrial use; Annex XVII organotin restrictions target skin/food-contact articles, not industrial catalysts.
DBTDL Specification Sheet
| Property | Specification | Test Method |
|---|---|---|
| Chemical name | Dibutyltin dilaurate | — |
| CAS number | 77-58-7 | — |
| Molecular formula | C₃₂H₆₄O₄Sn | — |
| Molecular weight | 631.6 g/mol | — |
| Active content | ≥97% | Titration vs. KIO₃ |
| Tin (Sn) content | 18.0–18.5% | ICP-OES |
| Appearance | Clear pale-yellow liquid | Visual |
| Density (20°C) | 1.04–1.06 g/cm³ | ASTM D1475 |
| Refractive index (25°C) | 1.468–1.471 | ASTM D1218 |
| Water content | ≤0.1% | Karl Fischer |
| APHA colour | ≤100 | ASTM D1209 |
| Flash point | >225°C (closed cup) | ASTM D93 |
| Solubility | Soluble in toluene, xylene, IPA, MEK; insoluble in water | — |
| Packaging | 25 kg HDPE jerrycan / 200 kg lined steel drum | — |
| Shelf life | 12 months sealed below 25°C | — |
FAQ
+How much DBTDL for a typical alkoxy-cure RTV-1 sealant?
0.10–0.20% with MTMS crosslinker at 3–5% on α,ω-dihydroxy-PDMS base gives 25–40 min tack-free at 23°C/50% RH, full cure within 7 days.
+Why does my DBTDL turn cloudy after storage?
Partial hydrolysis from moisture exposure — tin oxide hydrates and free lauric acid form. Re-seal under nitrogen, run Sn assay; if below 17%, dispose the lot.
+Is DBTDL still allowed under EU REACH?
Yes. CAS 77-58-7 is registered for industrial silicone and PU catalysis. Annex XVII restrictions target skin/food-contact articles. For consumer skin-contact silicone, specify T-9 stannous octoate or Karstedt platinum.